1. Field of the Invention
The present invention relates to a television and more particularly, to a method for composing television caption data.
2. Discussion of the Related Art
Digital broadcastings are currently being transmitted and tested on televisions using ground waves. Accordingly, digital television (DTV) receivers have been developed and are continuously being improved to provide digital broadcasting to viewers. Compared to an analog TV receiver, a DTV receiver allows a larger screen, a higher resolution, and a faster data transmission.
Digital broadcasting data generally includes video data, audio data, and caption data. Here, the caption data with the latest technology in DTV broadcasting systems provide a wider service than the NTSC broadcasting systems of analog TVs. Particularly, digital television closed captions (DTVCC) have a transmission rate ten times faster than the NTSC captions such that multiple languages can simultaneously be transmitted. A standard regulation on the DTVCC is disclosed in the Caption Standard EIA 708 A.
FIG. 1 shows a general packet structure of a TV caption data including the DTVCC data. Referring to FIG. 1, a packet 1 includes a packet header 11 and a packet body 12. The packet body 12 is organized into a plurality of service blocks 2xcx9c5, where each of the service blocks 2xcx9c5 respectively includes a service block header 13, 15, 17, or 19 and a service block data 14, 16, 18, or 20. Here, the different services may be captions in different languages or captions in a same language but with different levels of difficulty. Therefore, a packet may include a plurality of services.
Accordingly, the packet 1 in FIG. 1 includes four services 2xcx9c5 with numbers 1xcx9c4. Here, the packet 1 may transmit one or more of standard service numbers 1xcx9c6 and/or one or more of extended service numbers 7xcx9c63. A packet generally transmits a minimum of four services. Also, various information can be used as codes for caption information to provide caption services. In particular, caption commands and caption characters or symbols are typically used.
The caption commands includes information on how the caption services are to be displayed on the actual screen while the caption characters or symbols are the content to be displayed. As the appearance and content varies, the caption information may have different lengths. Generally, characters are represented with one byte and commands are represented with more than two bytes. Contents on corresponding codes are disclosed in a coding map in the Caption Standard EIA 708 A.
The caption information as described can be transmitted through two packets if, for example, the caption information of more than two bytes are transmitted through different service block data. For example, a first packet may include the caption command and the second packet may include the caption characters or symbols. In such case, if a user switches on the caption function when the second of the two packet is being transmitted, the second packet does not include information which links to the information in the first packet. Thus, a decoder of the receiver considers a portion of the caption information included in the second packet as a code of a new command. Moreover, the decoder considers the command included in the first packet as a code for a new and different command. Accordingly, data such as following parameters are incorrectly decoded and the receiver cannot properly provide a caption service.
An object of the present invention is to solve at least the problems and disadvantages of the related art.
Another object of the present invention is to provide a more efficient TV caption service.
A further object of the present invention is to provide caption data and method to reduce errors in a decoder of a TV receiver.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purposes of the invention, as embodied and broadly described herein, a method for generating TV caption data includes checking the amount of block data remaining in a first of two packets assigned for use as DTV caption data, when a caption information is to be input to the first packet; comparing the size of the remaining block in the first packet with the size of the caption information; inputting the caption information in the remaining block of the first packet and transmitting the caption information to a TV receiver, if the size of the caption information is smaller than the size of the remaining block of the first packet; and inputting the caption information to a second packet and transmitting the caption information to the TV receiver, if the size of the caption information is larger than the size of the remaining block of the first packet.
According to the present invention, if there are more than two packets for use as TV caption data, each packet would include the full caption information, independently from the other packets.